$ GIT_TRACE_PERFORMANCE=true git gc
20:18:19.499676 trace.c:414 performance: 0.374835000 s: git command: 'git' 'pack-refs' '--all' '--prune'
20:18:19.845585 trace.c:414 performance: 0.343020000 s: git command: 'git' 'reflog' 'expire' '--all'
Counting objects: 170994, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (43413/43413), done.
Writing objects: 100% (170994/170994), done.
Total 170994 (delta 126176), reused 170524 (delta 125706)
20:18:23.567927 trace.c:414 performance: 3.715349000 s: git command: 'git' 'pack-objects' '--keep-true-parents' '--honor-pack-keep' '--non-empty' '--all' '--reflog' '--unpack-unreachable=2.weeks.ago' '--local' '--delta-base-offset' '.git/objects/pack/.tmp-49190-pack'
20:18:23.584728 trace.c:414 performance: 0.000910000 s: git command: 'git' 'prune-packed'
20:18:23.605218 trace.c:414 performance: 0.017972000 s: git command: 'git' 'update-server-info'
20:18:23.606342 trace.c:414 performance: 3.756312000 s: git command: 'git' 'repack' '-d' '-l' '-A' '--unpack-unreachable=2.weeks.ago'
Checking connectivity: 170994, done.
20:18:25.225424 trace.c:414 performance: 1.616423000 s: git command: 'git' 'prune' '--expire' '2.weeks.ago'
20:18:25.232403 trace.c:414 performance: 0.001051000 s: git command: 'git' 'rerere' 'gc'
20:18:25.233159 trace.c:414 performance: 6.112217000 s: git command: 'git' 'gc'